Not Applicable.
The present invention relates to a surgical retractor assembly and more particularly to a retractor assembly useful in surgery involving bones or hard tissue structures, such as in spine or joint surgery.
In many surgical operations it is customary to employ a retraction apparatus in which a frame or mounting ring rests over the patient surrounding the surgical opening, and a number of retractors may be movably attached to the frame and flexibly positioned, with various clamping or positioning mechanisms, to reach into the surgical opening and retract surrounding or obstructing tissue or organs, or to stabilize or position tissue or organs that are being worked on. In general, such retractors may include a blade or spoon-like member, or various gripping members, that each extend from an elongated handle or stem, and the stem moves within a clamping mechanism that mounts on the mounting ring and locks the blade or gripping member in a selected position. The clamping mechanism may itself have a mechanical structure allowing one or more additional degrees of movement in rotation or displacement, so that both the position and orientation of the blade may be quickly set and locked. Various common machine elements such as swivel ball mounts, arcuate rack or tilt mounts, rachet or rack adjustment and locking mechanisms, or screw clamps may be incorporated in the clamping structures to provide assemblies that are moved by hand into the desired position and locked.
By way of example, one commercially useful system is shown in the various patents of John R. Bookwalter, et al. such as U.S. Pat. Nos. 4,424,724; 4,254,763; 4,421,108; 5,375,481; and 5,520,608. This system is made and marketed by Codman. In the Bookwalter system, the frame element is a flat ring with regular notches. The ring is held by a post that clamps to the side rail of the operating table, so the ring is suspended in a plane above the surgical site. The plane of the ring sets one constraint on the movement of the retractor units, and allows the various retractor clamp assemblies to move into position and lock with a sliding movement that is conveniently set with one hand.
Many other surgical equipment suppliers also make surgical retractor systems, which may, for example be distinguished by one or more novel blades, clamps or frames, by a dimension or shape adapting the system to a particular surgery, or by features such as a round clamping ring or linked ring segments, to achieve their positioning and retracting abilities.
In general, such systems are intended to efficiently perform their function of retracting or positioning tissue in the surgical arena in a manner that allows simple adjustment with few motions by the surgeon during the course of a procedure, and without interfering with or obstructing the access lines necessary for manipulation within the surgical arena. In effect, a surgical retractor system requires a high degree of versatility to reach to and to retract or reposition, various tissues or organs as the surgical procedure proceeds. To a large extent, when it is simply a question of retracting soft tissue structures during abdominal or thoracic surgery, the required tasks can be performed with a set of just a few contoured blades having various lengths that extend proximate to the surgical opening as shown in the aforesaid patents. However, when the tissue does not consist of soft organs or structures spaced about a large opening but instead requires retraction of muscle or connective tissue from bony structures, the alignment of the blade with the tissue becomes more difficult, and it may be awkward to correctly insert or align the available clamping structures and retraction blades with the intended tissue. This is especially true for operations in and around bones and joints.
Accordingly, it would be desirable to develop an improved surgical retractor blade.
It would also be desirable to develop a surgical retractor system useful for surgery on bones and joints.
It would also be desirable to develop a surgical retractor system useful for spinal surgery.
It would further be desirable to develop such a retractor blade which is also usable with existing clamps and rings.
One or more of the above desirable features are obtained with a basic embodiment of the present invention by providing a retractor blade with a controlled degree of self rotation such that the blade swings into alignment near a bone or hard tissue structure. The retractor blade includes a blade portion and a handle portion which may for example be integrally joined or may fit together in a modular way to allow different blades to be removably and interchangeably manually inserted into the handle assembly. The handle assembly in turn is configured so its stem slides back and forth within a ratcheting or similar multi-position locking mechanism to allow adjustment of the stem extension along one or more axes, and is rounded to effect a limited range of angular rotation of the blade about the stem axis.
In a preferred embodiment the retractor stem has a rounded cross-section of substantially circular shape with one or more protruding ridges extending along the axial direction such that the edge-to-edge thickness of the stem varies with angular position about the axis, from a free to a jammed state. The handle is configured to slide back and forth within a ratchet clamp mechanism and has a rack, thread or other stepped surface such that when inserted through the clamp mechanism a spring loaded pawl or locking lever locks the handle at a defined extensional length. Preferably, the ridges of the handle are equi-spaced around its circumference, and fit within a square passage such that the ridge-to-ridge stem diameter is greater than the width of the square channel and is less than its diagonal. As a result, the handle may rotate freely about its axis by an amount less than xcfx80/4, up to a point at which the ridges jam by interference against the walls of the passage. Preferably four ridges are spaced at 90xc2x0 intervals around the circumference, and are dimensioned such that the handle, when fitted through a conventional square passage clamp assembly rotates up to about 30xc2x0 to either side before jamming. The interference contact of ridges and wall thus limits the ability of the blade to swing sideways more than a limited amount, while allowing free movement as necessary for the surface of the blade to swing tangentially down to a position close to a hard tissue structure or bone, and to precisely reach and retract tissue, such as muscle or connective tissue, from the immediate vicinity thereof Most preferably, the ridges have an asymmetric ramp or slope, having a graded ascent with a sharp drop off after the peak, thus providing a smooth resistance up to the point of jamming, and well controlled release when it is necessary to remove the blade.
In a preferred embodiment the retractor blade assembly comprises a handle and a blade. The handle has a stem with a blade mounting block assembly secured to the end of the stem. The stem extends along an axis and the blade mounting block has a dovetail channel extending transverse to the axis. The blade is formed as a separate element, and is manually inserted into the mounting block to complete the retractor. Both the stem and the block are formed of a material such as stainless steel, while the blade may be formed of a material such as a suitable nylon, polyethylene or polycarbonate typically having lesser hardness or stiffness modulus, and suited as a disposable or single-use item. The proximal end of the blade has a shape matching the dovetail channel of the handle assembly, and is configured to manually press fit securely into the dovetail channel. Blades of different sizes between approximately 5 and 15 centimeters length are provided in a modular set so that a retractor blade may be selected and assembled during surgery to achieve the desired reach and scope of use for a particular retraction. Preferably the blade is formed of an unfilled polymer which is translucent to radiographic imaging energy, thus permitting unobstructed images to be made with the retractor in place. This embodiment is particularly advantageous for operations such as anterior approaches to the spine, or for operations such as joint surgery, where a view of the blade is occluded from one or more aspects.
The blade may be formed with its surface dished or curved in one or more directions, or may have a lip or flare adapted for penetrating or retracting a particular structure, such as tissue contacting the spine. The dovetail is configured such that the blade itself mounts in a plane substantially transverse or perpendicular to the retractor shaft. Rotation of the shaft then allows the blade to swing into different angular orientations within the plane of the blade, while the tip of the blade changes its vertical height or offset from the mounting ring. This is particularly advantageous for bringing the curved tip of the blade down under a cut edge of tissue in an essentially planar approach to retract the tissue from a bone, where blade movement parallel to the shaft axis would be impeded by the bone.